--- title: "CVE-2026-39830: golang.org/x/crypto: Invoking client can cause server deadlock on unexpected responses" url: https://erroneo.us/security/cve/CVE-2026-39830/ description: "CVE-2026-39830 (golang.org/x/crypto (Go)): A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the…" type: vulnerability-record section: "Security Digest" date_published: 2026-05-22 date_modified: 2026-09-18 publisher: erroneo.us author: erroneo.us Security Desk cve: "CVE-2026-39830" kev: false cvss: 7.5 epss: 0.00621 license: All rights reserved. Quote with attribution and a link. --- # CVE-2026-39830: golang.org/x/crypto: Invoking client can cause server deadlock on unexpected responses **Signal:** Normal patch cycle. No exploitation signal; fix it in your next routine update if you are affected. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.) ## Should you act? - No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected. - EPSS 0.6% , percentile 49: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 49% of all scored CVEs (low). EPSS is a probability, not a verdict. - Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it. - Only applies if your dependency tree includes golang.org/x/crypto (Go) < 0.52.0, fixed in 0.52.0 . Check your lockfile, including transitive dependencies. ## What it is A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop. The blocked goroutine could not be released by calling Close(), resulting in a resource leak per connection. Unsolicited global responses are now discarded. ## Affected packages - Go `golang.org/x/crypto` < 0.52.0 → fixed: 0.52.0 ## Affected products (CVE record) - golang.org/x/crypto golang.org/x/crypto/ssh: < 0.52.0 ## Severity - CISA-ADP CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H` - redhat-SADP CVSS 3.1: 7.5 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` - GitHub CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H` ## Exploitation - CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA). - CISA SSVC assessment: exploitation none , automatable yes , technical impact partial . - FIRST EPSS (model of 2026-10-21): 0.62% probability of exploitation activity in the next 30 days; percentile 49. ## Sources - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:41019) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:48151) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36796) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36199) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37072) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:35833) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:49944) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:67450) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:29455) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:54531) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:61314) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36808) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:66521) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:51033) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:59467) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:66022) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:43692) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:54400) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36319) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36625) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36207) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36651) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:40945) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:40118) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37275) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:60520) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36648) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:41036) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:57801) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:52857) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:52910) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:65964) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37387) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:41031) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:42146) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:43052) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:42796) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:41066) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:40262) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:40972) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:40974) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:40969) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:36797) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37271) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37268) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37272) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37278) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37286) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:37296) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:57194) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:46885) - [access.redhat.com](https://access.redhat.com/errata/RHSA-2026:47735) - [GitHub Advisory GHSA-vgwf-h737-ff37](https://github.com/advisories/GHSA-vgwf-h737-ff37) - [CVE.org record CVE-2026-39830](https://www.cve.org/CVERecord?id=CVE-2026-39830) - [NVD entry CVE-2026-39830](https://nvd.nist.gov/vuln/detail/CVE-2026-39830) - [go.dev](https://go.dev/issue/79564) - [groups.google.com](https://groups.google.com/g/golang-announce/c/a082jnz-LvI) - [go.dev](https://go.dev/cl/781640) - [go.dev](https://go.dev/cl/781664) - [pkg.go.dev](https://pkg.go.dev/vuln/GO-2026-5017) - [access.redhat.com](https://access.redhat.com/security/cve/CVE-2026-39830) - [RHBZ#2480684](https://bugzilla.redhat.com/show_bug.cgi?id=2480684) - [security.access.redhat.com](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39830.json) --- Source page: https://erroneo.us/security/cve/CVE-2026-39830/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt