nodemailer before 10.0.6 Denial of Service via addressparser

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

nodemailer before 10.0.6 contains a denial of service vulnerability in the addressparser free-text fallback regex pattern that exhibits quadratic backtracking behavior. Attackers can supply crafted email header values with long whitespace-free runs to block the Node.js event loop for tens of seconds, causing service unavailability.

Source published

26 Sep 2026 13:23:56 UTC

Source modified

28 Sep 2026 15:01:54 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nodemailer before 10.0.6 contains a denial of service vulnerability in the addressparser free-text fallback regex pattern that exhibits quadratic backtracking behavior. Attackers can supply crafted email header values with long whitespace-free runs to block the Node.js event loop for tens of seconds, causing service unavailability.

Source published

Sep 26, 2026, 1:23:56 PM (timezone not stated)

Source modified

Sep 28, 2026, 3:01:54 PM (timezone not stated)

Observed here

11 Nov 2026 05:27:39 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

nodemailer before 10.0.6 contains a denial of service vulnerability in the addressparser free-text fallback regex pattern that exhibits quadratic backtracking behavior. Attackers can supply crafted email header values with long whitespace-free runs to block the Node.js event loop for tens of seconds, causing service unavailability.

Source published

26 Sep 2026 14:16:55 UTC

Source modified

30 Sep 2026 16:32:17 UTC

Observed here

25 Oct 2026 04:17:26 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

### Summary When `addressparser` finds no address by its strict reading, it falls back to pulling one out of the free text with `/\s*\b[^@\s]+@[^\s]+\b\s*/`. That pattern backtracks quadratically: `[^@\s]+` is retried from every offset and rescans the run to the next `@` each time. A single header value holding a long whitespace-free run with no usable `@` blocks the Node.js event loop for tens of seconds. It is cheaper to exploit than GHSA-prgh-xp8r-p3m5: 273KB is enough for ~43s, where the comment-joined shape needed ~1.5MB for ~10s. ### Details The fallback in `src/addressparser/index.ts` ran the pattern as a search. `[^@\s]+` crosses neither whitespace nor `@`, so from each start offset it scans forward to the next `@` or to the end of the run and then fails, and the engine simply advances one character and repeats. Three shapes make every offset fail: - the run holds no `@` at all - the only `@` has nothing after it - the only `@` has nothing before it A fourth reaches it with a valid address present but placed past a long run, so the long run is walked before the match is found. ### PoC ```js const addressparser = require('nodemailer/lib/addressparser'); const s = Date.now(); addressparser(' >' + '>[x][x]'.repeat(40000)); // 273KB console.log(Date.now() - s, 'ms'); // ~43000 ms, blocking ``` Measured on 10.0.5: | Value | Parse time | | --- | --- | | `'[x]'.repeat(40000)` (117KB) | 9.0 s | | `'[x]'.repeat(40000) + '@'` (117KB) | 8.9 s | | `'@' + '[x]'.repeat(40000)` (117KB) | 8.8 s | | `' >' + '>[x][x]'.repeat(40000)` (273KB) | 42.9 s | ### Impact Algorithmic-complexity denial of service. Node is single threaded, so the block stalls the whole process. Reachable without authentication anywhere inbound header values are handed to this parser, mailparser being the notable case, and reachable from application input wherever a user-supplied string is used as a message address, since `mime-node` parses `to`, `from` and `cc` when composing. ### Patch The search is replaced by a single linear pass that finds the one offset the pattern can match at, which is then applied there with a sticky regex. Match results are unchanged, verified against the previous implementation over 3.4 million random strings comparing both the match offset and the matched text, plus 800k full-parse comparisons. Found while validating the report in GHSA-prgh-xp8r-p3m5, not reported externally.

Source published

29 Sep 2026 23:43:36 UTC

Source modified

30 Sep 2026 00:00:03 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH