CVE-2026-6103: Php5 · phar_tar_number() parses the octal size field of a TAR header into a uint32_t with no overflow
Affects php5Source GCVE Database
Not known to be exploited · CVSS 4.3 Medium · fixed in 5.5.9+dfsg-1ubuntu4.29+esm17 : update php5 when convenient.
Data as of 27 Oct 2026, 06:42 UTC
- Patch
- Available – fixed in 5.5.9+dfsg-1ubuntu4.29+esm17, 7.0.33-0ubuntu0.16.04.16+esm21, 7.2.24-0ubuntu0.18.04.17+esm13 +5
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 25 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10php8.5pkg:deb/ubuntu/php8.5?arch=source&distro=stonkingOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSphp8.5pkg:deb/ubuntu/php8.5?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSphp8.3pkg:deb/ubuntu/php8.3?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 22.04 LTSphp8.1pkg:deb/ubuntu/php8.1?arch=source&distro=jammyOther threats | Affected
| Fixed in
|
Ubuntu Pro 20.04 LTSphp7.4pkg:deb/ubuntu/php7.4?arch=source&distro=esm-infra/focalOther threats | Affected
| Fixed in
|
Ubuntu Pro 18.04 LTSphp7.2pkg:deb/ubuntu/php7.2?arch=source&distro=esm-infra/bionicOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
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.
References
- ubuntu.com/security/CVE-2026-6103 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-6103 (opens in a new tab)
- github.com/php/php-src/security/advisories/GHSA-j3wh-g957-2m85 (opens in a new tab)
- github.com/php/php-src/blob/php-8.4.26/NEWS (opens in a new tab)
- ubuntu.com/security/notices/USN-8936-1 (opens in a new tab)