[UPDATE] [high] HAProxy: Multiple vulnerabilities

highCVE-2026-55203 CVE-2026-55204

A remote, anonymous attacker can exploit multiple vulnerabilities in HAProxy to manipulate files or cause a Denial of Service.

CSIRTS triage

vendor: HAProxy product: HAProxy Denial of serviceOther

What: A remote, anonymous attacker can exploit multiple vulnerabilities in HAProxy to manipulate files or cause a Denial of Service.
Who is affected: Deployments of HAProxy are affected.
Urgency: Remediation is urgent due to the high severity and potential for significant impact.
Action: Update HAProxy to the latest version to mitigate these vulnerabilities.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: CERT-Bund (BSI) Security Advisories (DE · national-cert · site)
Severity: high
Published: 2026-07-09
Exploitation: Not in CISA KEV at last sync
Language: Machine-translated to English — verify against the original

Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-2012

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-552030.32% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 24% of all scored CVEs.
Low exploitation riskCVE-2026-552040.43% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 35% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-55203	coverage & exploitation status	NVD · CVE.org
CVE-2026-55204	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

unknownVulnerability in HAProxy (June 29, 2026)cert-fr-avis
highCVE-2026-55204: HAProxy - NULL Pointer Dereference in hpack_dht_insert Functionmsrc
highCVE-2026-55203: HAProxy - Integer Overflow in FCGI Demux Record Length Fieldmsrc

Recent advisories for HAProxy

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownVulnerability in HAProxy (June 29, 2026)cert-fr-avis · 2026-06-29
highGHSA-h2qv-fj59-j46j: Netty HAProxy: Unbalanced Reference Count in Nested PP2_TYPE_SSL TLV Parsing Leads to Mem…ghsa · 2026-06-11
highCVE-2026-55204: HAProxy - NULL Pointer Dereference in hpack_dht_insert Functionmsrc · 2026-06-09
highCVE-2026-55203: HAProxy - Integer Overflow in FCGI Demux Record Length Fieldmsrc · 2026-06-09