What is CVE-2026-34621?

CVE-2026-34621 is Acrobat Reader | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (CWE-1321). The supplied enrichment data classifies it as Unclassified mapped to CWE-1321 CWE-1321.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Yes: CISA KEV signal present. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

Is there a public exploit?

18 public PoC repositories reported; 2 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with Not reported where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-34621 using CVSS 8.6, EPSS 7%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Treat as emergency remediation because CISA KEV status is present. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

CISA KEVhighpublic exploit

CVE-2026-34621

CVE-2026-34621 — Acrobat Reader | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (CWE-1321)

Q: Is it in CISA KEV?

Yes. The supplied enrichment data lists CVE-2026-34621 in CISA KEV with required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Acrobat Reader versions 24.001.30356, 26.001.21367 and earlier are affected by an Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability that could result in arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

Published Apr 11, 2026Updated Aug 28, 2026Sources: NVD, Adobe (CNA), CISA, FIRST EPSS, GitHub, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Confirmed

CISA KEV, listed Apr 13, 2026

EPSS

ahead of 94% of scored CVEs

Affects

Adobe

6 products listed

CVSS base

8.6

high

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

Active

none · proof-of-concept · active

Automatable

can an attacker script all four kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

The vendor's own words where we have them.

Upgrade Acrobat DC to a fixed release (26.001.21411). Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Federal deadline Apr 27, 2026 — passed 144 days ago

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Treat as emergency remediation because CISA KEV status is present.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Adobe	Acrobat DC	0 to <= 26.001.21367	Vulnerable
Adobe	Acrobat DC	26.001.21411	Patched
Adobe	Acrobat Reader DC	0 to <= 26.001.21367	Vulnerable
Adobe	Acrobat Reader DC	26.001.21411	Patched
Adobe	Acrobat 2024	0 to <= 24.001.30356	Vulnerable
Adobe	Acrobat 2024	24.001.30362 (Win), 24.001.30360 (Mac)	Patched

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

High

Integrity

High

Scope

Changed

Attack Complexity

Low

Attack Vector

Local

Privileges Req

None

User Interaction

Required

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
8.6	CVSS 3.1	high	1.8	6	Adobe (CNA)

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-1321 · Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Modify Application Data:LIKELIHOOD:High
DoS: Crash, Exit, or Restart:LIKELIHOOD:High

Mitigation: By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.

Weakness & attack patterns

CWE-1321

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-1 · Accessing Functionality Not Properly Constrained by ACLsCAPEC-180 · Exploiting Incorrectly Configured Access Control Security LevelsCAPEC-77 · Manipulating User-Controlled Variables

T1574.010Hijack Execution Flow: ServicesFile Permissions Weakness

CISA KEV details

CISA lists a CVE here once it has evidence of exploitation against real targets.

CISAThat month →

Listed

Apr 13, 2026

Federal deadline

Apr 27, 2026

passed 144 days ago

Ransomware use

Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a date to argue against.

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

2 of the 5 sampled are weaponized

Exploit entries

Exploit-DB and CTI exploit indexes

Social mentions

Posts naming this CVE. Attention, not evidence of exploitation — it spikes on disclosure and decays whether or not anything is exploited.

35 more posts on this CVEShowing 5 of 40 · Who is discussing this CVE, and how loudlyUnlock free

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Monitor for scanner or exploit-pattern traffic after 18 public PoC repositories were reported.

Groups associated with this CVE

Groups reported in connection with this vulnerability. A reported association, not a confirmed observation of that group using it — and not scoped to any sector or campaign.

hashd4c9d9027326271a89ce51fcaf328ed673f17be33469ff979e8ab8dd501e664f46
SOCRadar Threat Exchange Services · Nov 5, 2025
hashbaea954b95731c68ae6e45bd1e252eb4560cdc4546
SOCRadar Threat Exchange Services · Nov 5, 2025
hash1d5920f4b44b27a802bd77c4f0536f5a46
SOCRadar Threat Exchange Services · Nov 5, 2025
hashffb6a787ef00e7c44500173b0a7aff45bbb65c8c8733a5870f15eeffda074a1e46
Public Sandbox Observables · Aug 11, 2026
hash5283c414bea2dd9b2f57fe1ee2386477c350827046
Public Sandbox Observables · Aug 11, 2026

5 more indicators on this CVEShowing 5 of 10 · Hashes, addresses and domains from a live threat exchangeUnlock free

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 8.6 (AV:L)
Aug 28, 2026 · NVD
Added to CISA KEV catalog
Apr 13, 2026 · CISA
Initial · CVE published
Apr 11, 2026 · NVD

Source activity

Readings a source repeats on a schedule, counted rather than listed.

29×SVRS was changedMay 14, 2026 – Jul 5, 2026 · SOCRadar CTI
9×TweetsMay 16, 2026 – Jun 16, 2026 · SOCRadar CTI
1×Github_Repos · Github repository created, azefzafyoussef/CVE-2026-34621May 12, 2026 · SOCRadar CTI

References

3 on the record

helpx.adobe.com/security/products/acrobat/apsb26-43.html
Vendor Advisory, NIST
www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-34621
US Government Resource, NIST
nvd.nist.gov/vuln/detail/CVE-2026-34621
Vendor Advisory

Coverage

20 stories from the feeds we poll

15 more reports on this CVEShowing 5 of 20 · Vendor research and security press coverageUnlock free

Elsewhere on this site

Adobeevery CVE for this vendor
April 2026what else CISA listed
Unclassifiedsame class
CWE-1321other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

Only the 5 indicator(s) reported for this CVE are available; no packet-level or host-forensic artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-34621 is Acrobat Reader | Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (CWE-1321), a high vulnerability affecting Acrobat DC, Acrobat Reader DC, Acrobat 2024 from Adobe. The current evidence lists it in CISA KEV, and the exploit status is: Yes: CISA KEV signal present. Public exploit evidence is: 18 public PoC repositories reported; 2 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 8.6 describes technical severity, while EPSS 7% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.