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🛡️ OESA-2026-1105 — mod-security-crs (CVE-2026-21876)

🔴 CVSS 9.5 — Critical ✅ No Known Exploit OSV
9.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

mod_security_crs security update

The base rules are provided for mod_security by this package.

Security Fix(es):

The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls. Prior to versions 4.22.0 and 3.3.8, the current rule 922110 has a bug when processing multipart requests with multiple parts. When the first rule in a chain iterates over a collection (like MULTIPART_PART_HEADERS), the capture variables (TX:0, TX:1) get overwritten with each iteration. Only the last captured value is available to the chained rule, which means malicious charsets in earlier parts can be missed if a later part has a legitimate charset. Versions 4.22.0 and 3.3.8 patch the issue.(CVE-2026-21876)

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity low, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Changed — a successful attack reaches components beyond the vulnerable one.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: Low — limited, and the attacker does not choose what is affected.
  • Availability impact: None.

Affected software

OESA-2026-1105 is recorded against 1 package.

  • mod-security-crs (fixed in 3.2.2-3.oe2203sp3)

Timeline and source

Published on 16 January 2026 and last revised on 18 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

www.openeuler.org (Advisory)
nvd.nist.gov (Advisory)

Other advisories for this package

mod-security-crs has other advisories on record. If you are patching this one, these are worth checking on the same host:

Details

Severity CRITICAL
CVSS Score 9.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-01-16
Updated 2026-08-20
Modified 2026-08-18
Fix URL N/A

Affected Packages

Software From version Fixed in
mod-security-crs — 3.2.2-3.oe2203sp3

Similar Threats

Exploit Protection

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OESA-2026-1105 carries CVSS 9.5 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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