CVE-2026-21876

mediumpriority · track · 37EPSS 0.179 · 97 %ileexploit · PoCDEEUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

4 exploits · PoC

Likely / severe?

17.9% (97th) EPSS

CVSS 5.3 · medium

Is it mine?

10 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · cert_bund · nvd

EPSS · scored 2026-10-27

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.

cvss

Technical severity, 0–10. One row per scoring source.

9.3

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–critical · 5–9.3

v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:Nprimary · NVD / NIST USexploitability 3.9 · impact 1.4

v3.19.3criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:Nsecondary · ENISA EU

v3.19.3criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:Nsecondary · security-advisories@github.comexploitability 3.9 · impact 4.7

v3.15mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:Psecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: yes · Technical Impact: partialcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-794US

exploits (4)

Public proof-of-concept and weaponised exploit code.

EDB-52558coreruleset 4.21.0 - Firewall BypassPoC · exploit_db
CVEs-Labs/CVE-2026-21876CVEs-Labs/CVE-2026-21876PoC · poc_in_github
Mefhika120/CVE-2026-21876CVE-2026-21876 OWASP ModSecurity CRS WAF bypass (docker container + minimal PoC).PoC · poc_in_github
daytriftnewgen/CVE-2026-21876CVE-2026-21876 PoC: WAF charset bypass (Flask, ASP.NET and Spring Boot stands)PoC · poc_in_github

affected products (10)

Products and version ranges known to be affected.

Kemp LoadMaster <7.2.63.1all versionscert_bundDE
Kemp LoadMaster LTSF <7.2.54.17all versionscert_bundDE
Progress Software MOVEit WAF <7.2.63.0all versionscert_bundDE
Kemp LoadMaster≤ LTSF <7.2.54.17cert_bundDE
Kemp LoadMaster< 7.2.63.1cert_bundDE
Progress Software MOVEit≤ WAF <7.2.63.0cert_bundDE
coreruleset coreruleset≤ < 4.22.0enisa_euvdEU
coreruleset coreruleset≤ < 3.3.8enisa_euvdEU
owasp owasp modsecurity core rule set< 3.3.8nvdUScpe:2.3:a:owasp:owasp_modsecurity_core_rule_set:*:*:*:*:*:*:*:*
owasp owasp modsecurity core rule set4.0.0 → 4.22.0nvdUScpe:2.3:a:owasp:owasp_modsecurity_core_rule_set:*:*:*:*:*:*:*:*

advisories (1)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2026-1185Kemp LoadMaster und Progress Software MOVEit WAF: Mehrere SchwachstellenDeutsch2026-04-20csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Kemp LoadMaster und Progress Software MOVEit WAF ausnutzen, um beliebigen Programmcode auszuführen oder Sicherheitsmaßnahmen zu umgehen.

also known as (2)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd cert_bund nvd NVD CVE.org MITRE

published 2026-01-08modified 2026-06-17

references (20)

External citations — patches, advisories, analysis.

scry

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