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No exploitation reportedFix available

CVE-2026-34180

Heap Buffer Over-read in ASN.1 Content Parsing

No exploitation reported by the sources we read.

  • Published2026-06-09
  • Fixed in3.6.3 · 3.5.7 · 3.4.6 · 3.0.21 · 1.1.1zh · 1.0.2zq
  • WeaknessCWE-125

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Issue summary: Parsing a crafted DER-encoded ASN.1 structure with a primitive element whose content exceeds 2 gigabytes in length may cause a heap buffer over-read on 64-bit Unix and Unix-like platforms. Impact summary: The heap buffer over-read may crash the application (Denial of Service) or to load into the decoded ASN.1 object contents of memory beyond the end of the input buffer. More typically such ASN.1 elements would instead be truncated. An integer truncation in OpenSSL's ASN.1 decoder causes the content length of an ASN.1 primitive element to be mishandled when it exceeds 2 gigabytes. In the worst case the truncated length is treated as a request to scan the binary content for a terminating zero byte, possibly causing OpenSSL to read either less than or beyond the end of the allocated buffer. Applications that pass attacker-supplied data to d2i_X509(), d2i_PKCS7(), or any other d2i_* decoding function are affected. OpenSSL's own command-line tools are not vulnerable, as data read through the BIO layer is checked before it reaches the affected code. The issue only affects 64-bit Unix and Unix-like platforms; 32-bit platforms and 64-bit Windows are not affected. The FIPS modules in 4.0, 3.6, 3.5, 3.4 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

Timeline

dates in UTC
  1. 2026-06-0917:17CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-34180?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-34180?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
OpenSSL
BranchAffectedFixed in
3.6≥ 3.6.0, < 3.6.33.6.3
3.5≥ 3.5.0, < 3.5.73.5.7
3.4≥ 3.4.0, < 3.4.63.4.6
3.0≥ 3.0.0, < 3.0.213.0.21
1.1≥ 1.1.1, < 1.1.1zh1.1.1zh
1.0≥ 1.0.2, < 1.0.2zq1.0.2zq
4.0= 4.0.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • opensslAlmaLinux:10all versions · fixed in 1:3.5.5-4.el10_2.alma.1and 3 other packages
  • opensslAlmaLinux:9all versions · fixed in 1:3.5.5-4.el9_8and 3 other packages

Vendor advisories

  • CVE-2026-34180 Red Hat Product Security208 products fixed · 53 known affected

    openssl: OpenSSL: Heap buffer over-read in ASN.1 decoding can lead to denial of service or information disclosure.

    edk2-aarch64 as a component of Red Hat Enterprise Linux 10 · edk2-ovmf as a component of Red Hat Enterprise Linux 10 · edk2-tools as a component of Red Hat Enterprise Linux 10 · +50 more

  • RHSA-2026:82888 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.17.2

  • RHSA-2026:82857 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

  • RHSA-2026:82372 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

  • RHSA-2026:82354 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

  • RHSA-2026:82347 Red Hat Product Security8 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

18 more advisories

Full record on NVD

Fix

  1. Update OpenSSL to 3.6.3 · 3.5.7 · 3.4.6 · 3.0.21 · 1.1.1zh · 1.0.2zq
  2. Vendor fix Red Hat Product Security RHSA-2026:82888 · 1 productBefore applying this update, make sure all previously released errata relevant to your system have been applied. The steps to apply the upgraded images are different depending on the installation plan approval policy you used when installing the cert-manager Operator for Red Hat OpenShift. - If t…
  3. Vendor fix Red Hat Product Security RHSA-2026:73982 · 1 productBefore applying the update, back up your existing Red Hat JBoss Web Server installation, including all applications and configuration files. The References section of this erratum contains a download link for the update. You must be logged in to download the update.
  4. Vendor fix Red Hat Product Security RHSA-2026:67551 · 3 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
  5. Vendor fix Red Hat Product Security RHSA-2026:58981 · 3 productsPlease consult the RHUI Technology Preview Release Notes at https://access.redhat.com/articles/7141172 for instructions on how to use this image set.
  6. Vendor fix Red Hat Product Security RHSA-2026:34102 · 2 productsThe Insights proxy container image provided here is downloaded by the Red Hat Insights proxy product RPM. Before applying this update, make sure all previously released errata relevant to your system have been applied.
  7. Vendor fix Red Hat Product Security RHSA-2026:29197 · 4 productsThe containers required to run Discovery can be installed through discovery-installer RPM. See the official documentation for more details.

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-06-09
Last Modified
2026-07-23
NVD status
Analyzed
MSRC Title
Heap Buffer Over-read in ASN.1 Content Parsing

Frequently asked questions

What is CVE-2026-34180?

Issue summary: Parsing a crafted DER-encoded ASN.1 structure with a primitive element whose content exceeds 2 gigabytes in length may cause a heap buffer over-read on 64-bit Unix and Unix-like platforms. Impact summary: The heap buffer over-read may crash the application (Denial of Service) or to load into the decoded ASN.1 object contents of memory beyond the end of the input buffer. More typically such ASN.1 elements would instead be truncated. An integer truncation in OpenSSL's ASN.1 decoder causes the content length of an ASN.1 primitive element to be mishandled when it exceeds 2 gigabytes. In the worst case the truncated length is treated as a request to scan the binary content for a terminating zero byte, possibly causing OpenSSL to read either less than or beyond the end of the allocated buffer. Applications that pass attacker-supplied data to d2i_X509(), d2i_PKCS7(), or any other d2i_* decoding function are affected. OpenSSL's own command-line tools are not vulnerable, as data read through the BIO layer is checked before it reaches the affected code. The issue only affects 64-bit Unix and Unix-like platforms; 32-bit platforms and 64-bit Windows are not affected. The FIPS modules in 4.0, 3.6, 3.5, 3.4 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

Is CVE-2026-34180 actively exploited?

Active exploitation of CVE-2026-34180 has not been confirmed. Its EPSS score was 1.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-34180?

CVE-2026-34180 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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