Bug 2451867 (CVE-2026-4926)

Summary: CVE-2026-4926 path-to-regexp: path-to-regexp: Denial of Service via crafted regular expressions
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: aazores, abarbaro, abrianik, abuckta, adudiak, alcohan, alizardo, anjoseph, anpicker, anthomas, aschwart, asoldano, ataylor, bbaranow, bdettelb, bmaxwell, boliveir, bparees, bstansbe, caswilli, cmah, dbosanac, dbruscin, dhanak, dkuc, dlofthou, doconnor, drosa, dschmidt, eaguilar, ebaron, ehelms, erezende, ewittman, fdeutsch, ggainey, ggrzybek, gmalinko, gparvin, hasun, ibek, istudens, ivassile, iweiss, janstey, jbalunas, jcantril, jchui, jfula, jhe, jkoehler, jlanda, jolong, jowilson, jprabhak, jreimann, jrokos, juwatts, jwong, kaycoth, kbempah, kshier, ktsao, kvanderr, lball, lphiri, manissin, mbarnett, mdessi, mhulan, mnovotny, mosmerov, mposolda, mrizzi, mstipich, msvehla, mwringe, nboldt, ngough, nipatil, nmoumoul, nwallace, nyancey, omaciel, ometelka, orabin, oramraz, osousa, pahickey, pantinor, parichar, pberan, pcattana, pcreech, pdelbell, pesilva, pjindal, pmackay, psrna, ptisnovs, rchan, rexwhite, rhaigner, rjohnson, rkubis, rmartinc, rojacob, rstancel, rstepani, sausingh, sdawley, simaishi, smaestri, smallamp, smcdonal, smullick, solenoci, ssilvert, stcannon, sthirugn, sthorger, stirabos, syedriko, tasato, teagle, thason, thjenkin, tmalecek, ttakamiy, vdosoudi, veshanka, vmuzikar, wtam, xdharmai, yguenane
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in path-to-regexp. A remote attacker could exploit this vulnerability by providing specially crafted input that generates a regular expression with multiple sequential optional groups. This leads to an exponential growth in the generated regular expression, causing a Denial of Service (DoS) due to excessive resource consumption.
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Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2452250, 2452251, 2452253, 2452258, 2452259, 2452260, 2452249, 2452252, 2452254, 2452255, 2452256, 2452257, 2452261, 2452262, 2452297    
Bug Blocks:    

Description OSIDB Bzimport 2026-03-26 20:03:51 UTC
Impact:

A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service.

Patches:

Fixed in version 8.4.0.

Workarounds:

Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.