Vulnerability record · CVE-2023-2650 · published 30 May 2023
CVE-2023-2650: OpenSSL ASN.1 Object Identifier Parsing Denial of Service
OOpenssl · Openssl
OpenSSL's OBJ_obj2txt() converts ASN.1 OBJECT IDENTIFIERs to text with O(n^2) complexity, so a sub-identifier of tens or hundreds of KiB causes very long processing delays. Applications using OBJ_obj2txt() directly, or OpenSSL 3.0+ subsystems OCSP, PKCS7/SMIME, CMS, CMP/CRMF, TS, or X.509 certificate processing without message size limits can be stalled. The result is a denial of service, not code execution or data exposure.
Description
Issue summary: Processing some specially crafted ASN.1 object identifiers or data containing them may be very slow. Impact summary: Applications that use OBJ_obj2txt() directly, or use any of the OpenSSL subsystems OCSP, PKCS7/SMIME, CMS, CMP/CRMF or TS with no message size limit may experience notable to very long delays when processing those messages, which may lead to a Denial of Service. An OBJECT IDENTIFIER is composed of a series of numbers - sub-identifiers - most of which have no size limit. OBJ_obj2txt() may be used to translate an ASN.1 OBJECT IDENTIFIER given in DER encoding form (using the OpenSSL type ASN1_OBJECT) to its canonical numeric text form, which are the sub-identifiers of the OBJECT IDENTIFIER in decimal form, separated by periods. When one of the sub-identifiers in the OBJECT IDENTIFIER is very large (these are sizes that are seen as absurdly large, taking up tens or hundreds of KiBs), the translation to a decimal number in text may take a very long time. The time complexity is O(n^2) with 'n' being the size of the sub-identifiers in bytes (*). With OpenSSL 3.0, support to fetch cryptographic algorithms using names / identifiers in string form was introduced. This includes using OBJECT IDENTIFIERs in canonical numeric text form as identifiers for fetching algorithms. Such OBJECT IDENTIFIERs may be received through the ASN.1 structure AlgorithmIdentifier, which is commonly used in multiple protocols to specify what cryptographic algorithm should be used to sign or verify, encrypt or decrypt, or digest passed data. Applications that call OBJ_obj2txt() directly with untrusted data are affected, with any version of OpenSSL. If the use is for the mere purpose of display, the severity is considered low. In OpenSSL 3.0 and newer, this affects the subsystems OCSP, PKCS7/SMIME, CMS, CMP/CRMF or TS. It also impacts anything that processes X.509 certificates, including simple things like verifying its signature. The impact on TLS is relatively low, because all versions of OpenSSL have a 100KiB limit on the peer's certificate chain. Additionally, this only impacts clients, or servers that have explicitly enabled client authentication. In OpenSSL 1.1.1 and 1.0.2, this only affects displaying diverse objects, such as X.509 certificates. This is assumed to not happen in such a way that it would cause a Denial of Service, so these versions are considered not affected by this issue in such a way that it would be cause for concern, and the severity is therefore considered low.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Automated analysis
medium priorityCVSS 6.5 medium with high EPSS, but impact is availability-only, no KEV listing, and TLS exposure is constrained by size limits and client-auth conditions.
What it is
OpenSSL's OBJ_obj2txt() converts ASN.1 OBJECT IDENTIFIERs to text with O(n^2) complexity, so a sub-identifier of tens or hundreds of KiB causes very long processing delays. Applications using OBJ_obj2txt() directly, or OpenSSL 3.0+ subsystems OCSP, PKCS7/SMIME, CMS, CMP/CRMF, TS, or X.509 certificate processing without message size limits can be stalled. The result is a denial of service, not code execution or data exposure.
Impact
An attacker can force excessive CPU consumption and long processing delays, degrading or halting the affected service. There is no confidentiality or integrity impact; only availability is affected.
Attack surface
Reached remotely by supplying a crafted ASN.1 OBJECT IDENTIFIER, typically inside a certificate, AlgorithmIdentifier, or protocol message. No authentication is required, but the CVSS vector indicates user interaction is needed (UI:R), and TLS exposure is limited by the 100KiB certificate chain limit and applies mainly to clients or servers with client authentication enabled.
Exploitation
Not listed in CISA KEV and no ransomware use is documented. EPSS is high (0.75116, 99.485th percentile), and references include multiple patch commits plus vendor and third-party advisories, but no public exploit is confirmed in the record.
What to do
- Upgrade OpenSSL to a version containing the fixes referenced in the OpenSSL security advisory and patch commits.
- Apply vendor updates for Debian, Gentoo, NetApp, SonicWall and other affected products listed in the advisories.
- Enforce message and certificate size limits on services that parse ASN.1, OCSP, PKCS7/SMIME, CMS, CMP/CRMF or TS data.
- Avoid calling OBJ_obj2txt() on untrusted input, or bound the size of sub-identifiers before conversion.
- Disable client certificate authentication where it is not required to reduce TLS exposure.
Detection
- Monitor for CPU spikes or long request processing times in services that parse certificates or ASN.1 messages.
- Log and alert on unusually large OBJECT IDENTIFIER sub-identifiers or oversized certificate/OCSP/CMS payloads.
- Track OpenSSL versions across hosts and flag systems still running vulnerable builds.
- Review application logs for repeated timeouts or stalls during certificate verification or message parsing.
This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.
Affected products
2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
Track CVE-2023-2650 inside VULONE
Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.
Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2023-2650), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.
