# CVE-2026-23490: pyasn1 has a DoS vulnerability in decoder > An attacker can cause memory exhaustion and denial of service in applications using the pyasn1 library by sending malformed RELATIVE-OID data. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 16 Jan 2026 - **Updated:** 17 Sep 2026 - **Also known as:** ALSA-2026:1903, ALSA-2026:1904, ALSA-2026:1905, ALSA-2026:1906, ALSA-2026:3354, ALSA-2026:3359, ALSA-2026:4146, BELL-CVE-2026-23490, CLEANSTART-2026-HB36492, CLEANSTART-2026-SZ54252, CLSA-2026-1774431305, DEBIAN-CVE-2026-23490, DLA-4463-1, DSA-6114-1, ECHO-8e45-690d-3026, GHSA-63vm-454h-vhhq, MGASA-2026-0020, MINI-crg5-hv84-x99w, MINI-frjp-8hfq-j942, MINI-fv46-gm49-5482, MINI-p834-79qr-96g5, MINI-rcv8-w337-8f7h, OESA-2026-1259, OESA-2026-1260, OESA-2026-1261, OESA-2026-1262, OESA-2026-1777, OESA-2026-1778, PYSEC-2026-1810, RHSA-2026:1903, RHSA-2026:1904, RHSA-2026:1905, RHSA-2026:1906, RHSA-2026:2221, RHSA-2026:2299, RHSA-2026:2300, RHSA-2026:2302, RHSA-2026:2303, RHSA-2026:2309, RHSA-2026:2453, RHSA-2026:2460, RHSA-2026:2483, RHSA-2026:2486, RHSA-2026:2712, RHSA-2026:2758, RHSA-2026:28042, RHSA-2026:3354, RHSA-2026:3359, RHSA-2026:4138, RHSA-2026:4139, RHSA-2026:4140, RHSA-2026:4141, RHSA-2026:4142, RHSA-2026:4143, RHSA-2026:4144, RHSA-2026:4145, RHSA-2026:4146, RHSA-2026:4147, RHSA-2026:4148, RLSA-2026:1903, RLSA-2026:1904, RLSA-2026:1905, RLSA-2026:1906, RLSA-2026:3354, RLSA-2026:3359, RLSA-2026:4146, ROOT-APP-PYPI-CVE-2026-23490, SUSE-SU-2026:0252-1, SUSE-SU-2026:0300-1, SUSE-SU-2026:0430-1, SUSE-SU-2026:20133-1, SUSE-SU-2026:20158-1, SUSE-SU-2026:20447-1, SUSE-SU-2026:20482-1, UBUNTU-CVE-2026-23490, USN-7975-1, USN-8134-1, openSUSE-SU-2026:20089-1 ## What is CVE-2026-23490? CVE-2026-23490 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 16 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.2, a Denial-of-Service issue has been found that leads to memory exhaustion from malformed RELATIVE-OID with excessive continuation octets. This vulnerability is fixed in 0.6.2. Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling) ## Which versions are affected by CVE-2026-23490? 3 open source packages ship an affected version, including pyasn1. It affects 2 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `pyasn1` | PyPI | From 0.6.1 | 0.6.2 | | `pyasn1` | PyPI | From 0.6.1 | 0.6.2 | | `pyasn1` | PyPI | From 0.6.1 | 0.6.2 | | `fence-agents-amt-ws` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-apc` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-apc-snmp` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-bladecenter` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-brocade` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-cisco-mds` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-cisco-ucs` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-drac5` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-eaton-snmp` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-emerson` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-eps` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-heuristics-ping` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-hpblade` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ibm-powervs` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ibm-vpc` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ibmblade` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ifmib` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ilo-moonshot` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ilo-mp` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ilo-ssh` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ilo2` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-intelmodular` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ipdu` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-ipmilan` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-lpar` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-mpath` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-nutanix-ahv` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-rhevm` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-rsa` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-rsb` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-sbd` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-scsi` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-virsh` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-vmware-rest` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-vmware-soap` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `fence-agents-wti` | AlmaLinux:10 | All versions | 4.16.0-13.el10_1.2 | | `python3-pyasn1` | AlmaLinux:10 | All versions | 0.6.2-1.el10_1 | Products: Debian Debian Linux, Pyasn1 Pyasn1. ## How do I fix CVE-2026-23490? Upgrade pyasn1 to 0.6.2 or later. ## Is CVE-2026-23490 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-23490 exists. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-23490 and fix it if it is affected. What it is: CVE-2026-23490 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 16 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-23490 exists. Affected packages and fixed versions: - pyasn1 (PyPI): affected from 0.6.1; fixed in 0.6.2 - pyasn1 (PyPI): affected from 0.6.1; fixed in 0.6.2 - pyasn1 (PyPI): affected from 0.6.1; fixed in 0.6.2 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-23490/ (Markdown: https://insights.sbomify.com/CVE-2026-23490/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23490 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23490 - OSV: https://osv.dev/vulnerability/CVE-2026-23490 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-23490/ Summaries are generated and may contain mistakes; the official description above is the record.