What is CVE-2026-6103?

CVE-2026-6103 is Phar TAR phar_tar_number() Integer Overflow - Archive Entry Injection. The supplied enrichment data classifies it as Memory Corruption mapped to CWE-190 Integer Overflow or Wraparound.

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-2026-6103. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-6103 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?

6 public PoC repositories reported; 0 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-2026-6103 using CVSS 4.3, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

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. 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.

mediumMemory Corruptionpublic exploit

CVE-2026-6103

CVE-2026-6103 — Phar TAR phar_tar_number() Integer Overflow - Archive Entry Injection

phar_tar_number() parses the octal size field of a TAR header into a uint32_t with no overflow check. The field is 11 octal digits wide and holds values up to 0x1FFFFFFFF, so a size above 0xFFFFFFFF silently wraps. The parser then skips the wrong number of data blocks and interprets attacker-controlled file content as the next TAR header, which lets a crafted archive inject entries that PharData reports and extracts as if they were genuine.

Published Sep 25, 2026Updated Sep 25, 2026Sources: NVD, PHP Group (CNA), GitHub, Red Hat (VEX)

Triage

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

Exploitation

Exploit code

public exploit, none observed

EPSS

Not scored

FIRST has not published a score

Affects

PHP Group

4 products listed

CVSS base

4.3

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

PoC

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 PHP to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

Red Hat VEX · CVE-2026-6103

fixed57affected304not affected0

vendor_fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/

no_fix_planned: Out of support scope

none_available: Fix deferred

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
PHP Group	PHP	8.2.* to < 8.2.34	Vulnerable
PHP Group	PHP	8.3.* to < 8.3.35	Vulnerable
PHP Group	PHP	8.4.* to < 8.4.26	Vulnerable
PHP Group	PHP	8.5.* to < 8.5.11	Vulnerable

Attack characteristics

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

Availability

None

Confidentiality

None

Integrity

Low

Scope

Changed

Attack Complexity

Low

Attack Vector

Local

Privileges Req

None

User Interaction

None

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
4.3	CVSS 3.1	medium	2.5	1.4	php.net (CNA), PHP Group (CNA), Red Hat (VEX)

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

Weakness & attack patterns

CWE-190Integer Overflow or Wraparound

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

CAPEC-100 · Overflow BuffersCAPEC-123 · Buffer Manipulation

Public exploit

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

Repositories

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 6 public PoC repositories were reported.

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 4.3 (AV:L)
Sep 25, 2026 · NVD
Initial · CVE published
Sep 25, 2026 · NVD

References

6 on the record

github.com/php/php-src/security/advisories/GHSA-j3wh-g957-2m85
Exploit, Third Party Advisory
access.redhat.com/errata/RHSA-2026:70720
Vendor Advisory
access.redhat.com/security/cve/CVE-2026-6103
Vendor Advisory
bugzilla.redhat.com/show_bug.cgi?id=2541638
Vendor Advisory
www.cve.org/CVERecord?id=CVE-2026-6103
Vendor Advisory
nvd.nist.gov/vuln/detail/CVE-2026-6103
NVD

Elsewhere on this site

PHP Groupevery CVE for this vendor
Memory Corruptionsame class
CWE-190other 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-2026-6103 is Phar TAR phar_tar_number() Integer Overflow - Archive Entry Injection, a medium vulnerability affecting PHP from PHP Group. 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-2026-6103. Public exploit evidence is: 6 public PoC repositories reported; 0 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 4.3 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.