# CVE-2026-27137: Incorrect enforcement of email constraints in crypto/x509

> Attackers can bypass email address constraints in certificate chains by exploiting incorrect enforcement logic in the Go crypto/x509 package.

- **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:** 6 Mar 2026
- **Updated:** 18 Sep 2026
- **Also known as:** AZL-79613, AZL-79628, BELL-CVE-2026-27137, BIT-golang-2026-27137, CLEANSTART-2026-CO42319, CLEANSTART-2026-EL50504, CLEANSTART-2026-HI32575, CLEANSTART-2026-IO14579, CLEANSTART-2026-JP32193, DEBIAN-CVE-2026-27137, ECHO-e795-05b7-fb74, GHSA-7hfw-r8qc-89v4, GO-2026-4599, MINI-24vg-xh97-x7fm, MINI-2762-369g-383c, MINI-27hc-f8r5-mh98, MINI-27rp-cg8h-8m9q, MINI-284p-cw8q-9p7v, MINI-28qx-4m2m-2rm9, MINI-29h7-2r7c-f4m9, MINI-2cr9-38gr-f656, MINI-2g86-8244-p3rg, MINI-2h4f-4v4v-ccfq, MINI-2mg7-q2q8-v3gc, MINI-2mqp-rmj9-vpjx, MINI-2p3p-2mv4-wfcw, MINI-2q6r-g772-fm89, MINI-2v3m-72rq-wg7j, MINI-3488-6m4r-ggc3, MINI-34gq-j282-h43f, MINI-34r7-4x8m-44g4, MINI-3767-rvx7-jwp6, MINI-3888-wjjr-q4g2, MINI-39cw-5mcp-mqwg, MINI-39h4-mv43-cc3f, MINI-3c2v-cmmf-m84p, MINI-3gq8-x2vc-83wp, MINI-3h46-mcc2-2q45, MINI-3jr2-rf4f-9f6c, MINI-3qj3-6m43-26x3, MINI-3v8h-4x9c-98mx, MINI-3w23-q4x5-8w22, MINI-3wq4-wgp4-r888, MINI-42mx-8588-6wx9, MINI-42q3-hx3w-hgjg, MINI-42xq-mg85-fjfj, MINI-47f8-2hg2-qq66, MINI-4jcf-52rm-g9wh, MINI-4xf4-vxfm-cvrg, MINI-4xxc-cjfp-mfvc, MINI-53mc-fq6g-rmpp, MINI-543f-45rg-jq7r, MINI-5454-cv59-x9g6, MINI-55f7-mmjr-7249, MINI-562w-876f-j475, MINI-5g7w-p99f-7www, MINI-5hf8-q5fw-mxm2, MINI-5j88-7w7j-53r3, MINI-5jr3-qcvx-2gjj, MINI-5p69-rv49-hfh5, MINI-5pw2-f5cm-7j92, MINI-5wf9-6fxf-7m4h, MINI-5wj6-w56g-fmp7, MINI-5xgx-5v5j-55mc, MINI-5xwh-786c-rvgh, MINI-6565-rrv9-ghwh, MINI-67c9-8cpj-wjqj, MINI-67m5-jm6x-wcq6, MINI-687g-6h96-5vjm, MINI-6c5f-3g8q-2wgx, MINI-6gjm-9fw7-7g3j, MINI-6qx2-4792-54gw, MINI-6r23-v26h-w5rm, MINI-6vxp-3wh5-2rpc, MINI-6x83-4r8q-m6wv, MINI-73m5-xv3h-wqgx, MINI-75r8-p6jc-qf97, MINI-766j-h8m8-v5hf, MINI-76f2-657w-623j, MINI-78m6-jg5p-rg83, MINI-7gpj-jw49-7qx7, MINI-7jcv-h3xx-46qm, MINI-7pv3-w92p-xgqc, MINI-7q8v-4j6m-j4qp, MINI-7qh7-r6pj-h99w, MINI-7rqf-hc9q-5r2x, MINI-7wjx-5xcc-p5j8, MINI-84cx-f3xj-rvqq, MINI-865x-872p-hf44, MINI-89xh-vrrq-jpgc, MINI-8gwx-xp4c-fv4p, MINI-8j87-4hpr-4q2v, MINI-8jqh-w2m4-875r, MINI-8p57-jjrq-63r5, MINI-8r6m-wfcp-pqpg, MINI-8r83-2hxp-fcwv, MINI-8v2r-5pw4-wrrg, MINI-8vfj-rjvr-q4cc, MINI-8w5p-vf5j-c4mm, MINI-8wgc-55hq-63cm, MINI-8wqp-x7c2-q73f, MINI-96cq-g9vm-9p97, MINI-96wm-rf7m-v524, MINI-9988-fm4g-x4xx, MINI-99cq-4gj8-43m5, MINI-9hcr-g99x-x5fp, MINI-9m8x-mpc9-62x4, MINI-9m9j-c9r5-x4c3, MINI-9mg8-rrvm-5h7p, MINI-9pmw-4crj-3xf3, MINI-9q7w-2mxq-jf58, MINI-9qgg-7hx9-c9wh, MINI-9vq5-mrg2-486q, MINI-c2p2-x48h-5925, MINI-c3p5-4376-pw2j, MINI-c3pv-22jh-5j5x, MINI-c3xm-7m2p-66c4, MINI-c487-vh7f-fcmj, MINI-c4v7-rpmx-hmf8, MINI-c55w-6ph2-247j, MINI-c6pm-5q98-9jpc, MINI-c78c-jmqc-rj25, MINI-cgcq-2jvw-4x2r, MINI-chg8-v79q-w6m8, MINI-cj2h-h8f7-8wq3, MINI-cmpf-jmw3-jwxv, MINI-crw5-97j9-j8p6, MINI-cvfg-28vq-xrw4, MINI-cvxj-fwff-3cmf, MINI-cwm6-phcm-5q64, MINI-cwpw-6qwf-fmfr, MINI-f27x-x5cq-xqcx, MINI-f52p-84r8-mwww, MINI-f5h5-pmp8-fmg5, MINI-f7g5-62ff-h8w4, MINI-f869-8p8g-chhx, MINI-f999-2q4w-vc2j, MINI-ffch-5hmg-q5pp, MINI-fgjc-89c2-5jrr, MINI-fmc7-744c-8vrr, MINI-fmxh-mp65-95q4, MINI-fp92-5x29-wfp5, MINI-fpqc-3vfv-97q9, MINI-frgc-mfvm-8cm5, MINI-fvh7-8r6x-5xc8, MINI-fxqm-23h6-ccq5, MINI-g5h6-g5p5-px7v, MINI-g649-3rr7-vx98, MINI-gh6h-wjx5-9cmw, MINI-gm23-wmq2-h6f2, MINI-gmf4-hw5v-j226, MINI-gp79-2vmm-pc93, MINI-gr8m-vhh3-6c5c, MINI-gwff-3hh2-6v2j, MINI-h27f-7f35-4xm9, MINI-h27v-p7hc-9w72, MINI-h39m-gx3p-q297, MINI-h6f8-v63c-75rv, MINI-h9gp-r3wv-wc2p, MINI-h9wj-vmvr-qv2m, MINI-hcwr-2g5q-x8q4, MINI-hfhg-rwc2-j49v, MINI-hhw9-wxgp-wwq5, MINI-hm44-rf23-338f, MINI-hrhv-47g2-5jq7, MINI-hrm5-4hjm-cmh8, MINI-hrp3-rp9j-xpfp, MINI-hvmf-qrq9-hg8h, MINI-j244-4wvf-q834, MINI-j265-wrrf-3cw5, MINI-j2f5-qqcw-g48r, MINI-j3fx-xjx6-3hv4, MINI-j42r-94m5-hf3f, MINI-j5vc-4c9g-49wv, MINI-j768-7mg7-x74p, MINI-j7r9-c6rm-8m23, MINI-j7wq-f5p4-g2mx, MINI-jcgr-m9v3-3pj2, MINI-jf58-6hj3-8879, MINI-jh9q-4g28-w7mq, MINI-jq55-cw3p-fqm6, MINI-jq7f-m866-mg4x, MINI-jqcq-7fp2-jcvx, MINI-jvwq-r35g-mrvc, MINI-jx3m-q9ww-8655, MINI-jxjw-wfp6-6m2c, MINI-m2f8-pg6c-x82g, MINI-m2j8-vvfc-f7xj, MINI-m33x-97pw-c6qf, MINI-m4r2-c746-5v59, MINI-m57j-w4xf-5q2q, MINI-m6hp-jq7q-gmjg, MINI-m6hq-6j8r-xxh7, MINI-m857-cjmf-vh53, MINI-mfh9-cj8c-m49m, MINI-mg9h-p3hv-54mp, MINI-mgj7-pgxg-xq64, MINI-mj73-q4j3-gx7r, MINI-mjw6-3jx8-4mqm, MINI-mmfq-2cm2-335w, MINI-mp82-q59v-3rrc, MINI-mv4r-322v-hr69, MINI-mvgv-w97g-hm2h, MINI-mw87-68gp-ggc2, MINI-mwp7-mfw9-p223, MINI-mww6-x6rf-7mjh, MINI-p582-39g2-hwpg, MINI-p724-4fwg-x86j, MINI-p72m-vwhm-gcgh, MINI-p7q2-j775-56f3, MINI-p7v2-4cj9-mvhr, MINI-p9xm-jfgq-wq9h, MINI-pc5f-cg5m-cgcv, MINI-pfpj-pvr7-f954, MINI-pg6w-2xx5-59hg, MINI-ph2f-7hcc-54cw, MINI-phwq-r3x8-w4vj, MINI-pjpw-j2q9-3j7q, MINI-pjxg-pv2v-9jcf, MINI-pq87-v7q4-4v58, MINI-pr75-49gj-g89x, MINI-pvrc-rpch-c523, MINI-pxw9-7jhp-522v, MINI-q252-h727-3jrw, MINI-q3m5-qq49-3246, MINI-q4m8-cwhm-j964, MINI-q7pp-7g5v-h7x5, MINI-q855-89xp-hwc4, MINI-qgr9-957p-qgf4, MINI-qh9m-p6vr-8xhj, MINI-qhcw-7v4g-p32f, MINI-qqxc-545q-qmgm, MINI-qvgv-9h8x-96rr, MINI-qw3p-8j66-g3f4, MINI-qxqc-cfjv-q2gp, MINI-r26j-m9qf-7qc4, MINI-r2rg-96m7-59cf, MINI-r2rq-mpcf-7q8m, MINI-r2v3-86mw-mmc5, MINI-r3w7-mgmm-j4xp, MINI-r7c6-f68v-4pf8, MINI-r7xw-v8p9-2h2c, MINI-r8wj-pf27-c489, MINI-rf2c-7c3q-hmxr, MINI-rf7g-5x4h-qj4f, MINI-rgqx-2r79-86gh, MINI-rhx8-5vxp-mp65, MINI-rj7r-mhm7-8xmv, MINI-rmr9-88f5-267q, MINI-rp85-4782-p8fw, MINI-rpw5-jxcp-wphw, MINI-rvjq-gpv6-86ch, MINI-rx3v-gfp8-9jqm, MINI-rxrp-c4cx-6x35, MINI-v2f3-69w3-53xc, MINI-v2g2-mcjw-f96h, MINI-v3f5-64vg-hc27, MINI-v9qf-h57j-4cj4, MINI-vf4h-fx5c-xm3c, MINI-vfqc-xfj9-7hvj, MINI-vg9w-4fpq-rhv2, MINI-vgrj-fx8w-j4rh, MINI-vj8w-vw2p-fh68, MINI-vmf3-c46w-85xm, MINI-vmpm-m9p4-3vj5, MINI-vq99-jvj8-x8p9, MINI-vrf9-5pq5-9922, MINI-vw2w-6372-q4jw, MINI-vxff-cwp2-c8mx, MINI-vxjg-rgm2-hf32, MINI-w2w3-86q7-ghpv, MINI-w3cx-v94r-v958, MINI-w9r8-49vh-7h3x, MINI-wgjx-wf79-92p9, MINI-wh76-qfrf-74vw, MINI-wjxm-h3v8-xhrr, MINI-wmv8-6mfp-4jwv, MINI-wp3v-j537-6fpj, MINI-wp4m-95rc-9q2h, MINI-wqcq-3ggf-92f8, MINI-wvc9-vxxv-fmw7, MINI-wx5q-m9hh-9966, MINI-x28c-p83q-45qr, MINI-x28r-4rv5-9rq5, MINI-x2jv-3r6w-frf4, MINI-x394-hhg7-qgxw, MINI-x3fm-j8qh-gmwr, MINI-x452-c562-6rf7, MINI-x4p4-8gmp-337g, MINI-x72g-cq36-qrf9, MINI-x9c9-hxwj-vwv5, MINI-xf3x-rx6q-268v, MINI-xg79-vvw7-2cw4, MINI-xh6r-mjqx-7hc6, MINI-xm46-qqcv-vr4p, MINI-xmg6-27p5-wc82, MINI-xp96-4qrf-xr99, MINI-xr54-9988-6vg9, MINI-xv47-p222-wwc7, MINI-xvcp-44wv-wjpp, MINI-xvqc-459x-vf35, UBUNTU-CVE-2026-27137, openSUSE-SU-2026:10909-1

## What is CVE-2026-27137?

CVE-2026-27137 is a high-severity vulnerability in Golang Go, published on 6 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

When verifying a certificate chain which contains a certificate containing multiple email address constraints which share common local portions but different domain portions, these constraints will not be properly applied, and only the last constraint will be considered.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-27137?

2 open source packages ship an affected version, including golang and stdlib. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `golang` | Bitnami | From 1.26.0-0 | 1.26.1 |
| `stdlib` | Go | From 1.26.0-0 | 1.26.1 |
| `kubelogin` | openSUSE:Tumbleweed | All versions | 0.2.18-1.1 |

Products: Golang Go.

## How do I fix CVE-2026-27137?

Upgrade golang to 1.26.1 or later.

## Is CVE-2026-27137 being exploited?

There is no known exploitation of CVE-2026-27137 in the wild and no public exploit code.

## Other vulnerabilities in Golang Go

- [CVE-2020-0601](https://insights.sbomify.com/CVE-2020-0601/): Microsoft Windows CryptoAPI Spoofing (high 8.1, exploited in the wild)
- [CVE-2026-27143](https://insights.sbomify.com/CVE-2026-27143/): Missing bound checks can lead to memory corruption in safe Go in cmd/compile (critical 9.8)
- [CVE-2024-24790](https://insights.sbomify.com/CVE-2024-24790/): Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip (critical 9.8)
- [CVE-2023-39320](https://insights.sbomify.com/CVE-2023-39320/): Arbitrary code execution via go.mod toolchain directive in cmd/go (critical 9.8)
- [CVE-2023-24540](https://insights.sbomify.com/CVE-2023-24540/): Improper handling of JavaScript whitespace in html/template (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27137 and fix it if it is affected.

What it is: CVE-2026-27137 is a high-severity vulnerability in Golang Go, published on 6 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-27137 in the wild and no public exploit code.

Affected packages and fixed versions:
- golang (Bitnami): affected from 1.26.0-0; fixed in 1.26.1
- stdlib (Go): affected from 1.26.0-0; fixed in 1.26.1

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-2026-27137/ (Markdown: https://insights.sbomify.com/CVE-2026-27137/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27137
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27137
- OSV: https://osv.dev/vulnerability/CVE-2026-27137

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27137/
Summaries are generated and may contain mistakes; the official description above is the record.