Bug 2543247 (CVE-2026-75805)

Summary: CVE-2026-75805 openssl: openssl: Denial of Service via crafted CMP certificate revocation response
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abarbaro, akhatavk, alizardo, anthomas, aos-team-art-private, asdas, csutherl, dpaolell, dschmidt, ehelms, ggainey, ikhan, jchui, jclere, jdelft, jhe, jlanda, jpasqual, jupierce, juwatts, kshier, ktsao, lgarciaa, mbiarnes, mdellweg, mhulan, nboldt, nmoumoul, oaljalju, osousa, pcreech, pjindal, plodge, ppalepu, ppostler, prdhamdh, psrna, rbobbitt, rchan, rhel-process-autobot, sghai, sidsharm, simaishi, smallamp, stcannon, suppawar, szappis, tmalecek, vchlup, vlaad, watson-tool-maintainers, yguenane
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in OpenSSL. When a Certificate Management Protocol (CMP) client requests certificate revocation using a PKCS#10 Certificate Signing Request (CSR), it omits the certificate issuer name and serial number. A malicious or compromised CMP server, or an attacker possessing valid message protection credentials, can exploit this flaw by returning a crafted revocation response. This triggers a NULL pointer dereference when the client attempts to compare response data, causing the client application to crash and resulting in a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2544585, 2544586, 2544587    
Bug Blocks:    

Description OSIDB Bzimport 2026-09-29 15:52:59 UTC 
Issue summary: A CMP client that requests certificate revocation on the basis
of a PKCS#10 CSR may dereference a NULL pointer and terminate abnormally when
processing a crafted revocation response. 

Impact summary: The NULL pointer dereference happens on a read which 
leads to a crash and a Denial of Service for the affected client application.

CWE: CWE-476: NULL-pointer dereference

Description: A CMP client revoking a certificate has to tell the server which
certificate to revoke, and may do so by supplying a PKCS#10 CSR instead of the
certificate itself or its issuer name and serial number. This is
'openssl cmp -cmd rr -csr <file>' on the command line, or
OSSL_CMP_exec_RR_ses() with the certificate supplied via
OSSL_CMP_CTX_set1_p10CSR() through the API.

A CSR does not contain the issuer name and serial number of the certificate,
so the client does not send them. A server may optionally name the
certificate it revoked in its response, and the client then compares that
name against what it sent. Having sent neither an issuer name nor a serial
number, it has nothing to compare against, and a server returning a specially
crafted name causes the client to read from a NULL pointer and crash.

The revocation response is checked for valid message protection before
the affected code is reached, so an attacker must be a malicious or
compromised CMP server, or a man-in-the-middle in possession of the
secret used for message protection. Clients that identify the certificate
to be revoked by a certificate or by issuer and serial number rather
than by a PKCS#10 CSR are not affected.

FIPS impact: no
No FIPS modules are affected by this issue, as the CMP protocol
implementation is outside the OpenSSL FIPS module boundary.