What is CVE-2026-93421?

CVE-2026-93421 is Mesop: Unauthenticated ANSI Escape Sequence Injection in CSP Reporting Endpoint. The supplied enrichment data classifies it as Injection mapped to CWE-117 CWE-117; CWE-150 CWE-150.

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?

Active exploitation is not confirmed from current sources for CVE-2026-93421. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-93421 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

A public PoC is not confirmed from current sources for CVE-2026-93421. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS, database audit logs 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-2026-93421 using CVSS 5.3, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

Workarounds are not confirmed from current sources. 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. Prioritize based on EPSS, PoC availability, and external exposure. 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.

mediumInjection

CVE-2026-93421

CVE-2026-93421 — Mesop: Unauthenticated ANSI Escape Sequence Injection in CSP Reporting Endpoint

Mesop is a Python-based UI framework that allows users to build web applications. Prior to 1.3.4, the unauthenticated /__csp__ endpoint passes attacker-controlled document-uri, blocked-uri, and violated-directive values to the csp_report handler in mesop/server/static_file_serving.py, which prints them to standard output without neutralizing terminal control sequences. When an operator views the resulting logs in an ANSI-capable terminal, injected ANSI or VT100 sequences can clear or reposition the display, hide text, or present forged messages, reducing the integrity of monitoring and incident-response output. This issue is fixed in version 1.3.4.

Published Sep 23, 2026Updated Sep 23, 2026Sources: NVD, mesop-dev (CNA), GitHub, GitHub Security Advisory

Triage

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

Exploitation

Unreported

no source claims exploitation

EPSS

Not scored

FIRST has not published a score

Affects

mesop-dev

2 products listed

CVSS base

5.3

medium

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

None

none · proof-of-concept · active

Automatable

can an attacker script all four kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

The vendor's own words where we have them.

Upgrade mesop to 1.3.4 or later (pip advisory GHSA-g7f6-rxc4-qhph).

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.
Prioritize based on EPSS, PoC availability, and external exposure.
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
mesop-dev	mesop	< 1.3.4	Vulnerable
pip	mesop	<= 1.3.3	Vulnerable

Attack characteristics

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

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

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
5.3	CVSS 4.0	medium	—	—	mesop-dev (CNA)

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

Weakness & attack patterns

CWE-117
CWE-150

Inferred from the weakness class — not observed against this CVE.

CAPEC-66 · SQL InjectionCAPEC-7 · Blind SQL Injection

T1070Indicator Removal on Host
T1562.002Impair Defenses: Disable Windows Event Logging
T1562.003Impair Defenses: Impair Command History Logging

Detection

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

Search application, proxy, and WAF logs for requests touching /__csp__, /server/static_file_serving.py.
Prioritize edge telemetry for network-reachable mesop.

web/proxy/WAF logsapplication logsnetwork IDS/IPSdatabase audit logs

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 5.3 (AV:N)
Sep 23, 2026 · NVD
Initial · CVE published
Sep 23, 2026 · NVD
Added · GHSA-g7f6-rxc4-qhph published (medium)
Sep 23, 2026 · GitHub Security Advisory

References

5 on the record

github.com/mesop-dev/mesop/commit/f38c42a1d3eba246941ef8d7f645072d53c58785
Exploit, Third Party Advisory
github.com/mesop-dev/mesop/pull/1397
Exploit, Third Party Advisory
github.com/mesop-dev/mesop/releases/tag/v1.3.4
Exploit, Third Party Advisory
github.com/mesop-dev/mesop/security/advisories/GHSA-g7f6-rxc4-qhph
Exploit, Third Party Advisory
github.com/advisories/GHSA-g7f6-rxc4-qhph
Exploit, Third Party Advisory

Elsewhere on this site

mesop-devevery CVE for this vendor
pipevery CVE for this vendor
Injectionsame class
CWE-117other 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.

No confirmed IOCs, IP addresses, domains, file hashes, or malware 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-2026-93421 is Mesop: Unauthenticated ANSI Escape Sequence Injection in CSP Reporting Endpoint, a medium vulnerability affecting mesop from mesop-dev, pip. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-93421. Public exploit evidence is: A public PoC is not confirmed from current sources for CVE-2026-93421. 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 5.3 describes technical severity, while EPSS 0% 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.