Bug 2490897 (CVE-2026-9375)

Summary: CVE-2026-9375 urllib3: urllib3: Denial of Service via decompression bomb bypass with Brotli support
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerability-draftAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: abarbaro, adinn, agarcial, akhatavk, akostadi, alebedev, alinfoot, alizardo, amasferr, amctagga, anpicker, ansmith, anthomas, anujha, aoconnor, aos-team-art-private, aprice, asdas, asegurap, asoldano, bbaranow, bbrownin, blitton, bmaxwell, bniver, bparees, brasmith, bstansbe, cahl, cmyers, cochase, crizzo, dfreiber, dkeler, dlofthou, dmayorov, dnakabaa, doconnor, dpaolell, dranck, drow, dschmidt, dtrifiro, dymurray, eborisov, ebourniv, eglynn, ehelms, flucifre, fzakkak, galder, gbenhaim, ggainey, gmeno, gparvin, groman, gtanzill, hasun, hoberger, ibolton, ilpinto, istudens, ivassile, iweiss, jbalunas, jbritton, jburrell, jbuscemi, jchui, jdelft, jdobes, jfula, jhe, jholecek, jjoyce, jlanda, jlledo, jmatthew, jmitchel, jmontleo, jowilson, jpasqual, jpretori, jsamir, jschluet, jupierce, juwatts, jwong, kaycoth, kbempah, kgaikwad, kshier, ktsao, lball, lbrazdil, lcouzens, lgarciaa, lhh, ljawale, lpele, ltomasbo, mbabacek, mbarnett, mbenjamin, mbiarnes, mburns, mdellweg, mgarciac, mhackett, mhayden, mhulan, mminar, mosmerov, mrunge, msilmser, msvehla, nboldt, ngough, niyer, nmoumoul, nwallace, nyancey, oaljalju, oezr, olubyans, omaciel, ometelka, orabin, osousa, pakotvan, pantinor, pberan, pcreech, pesilva, pgaikwad, pjindal, pmackay, ppalepu, ppostler, prdhamdh, prwatson, psrna, ptisnovs, rbiba, rchan, rekumar, rhaigner, rhel-process-autobot, rjohnson, rstancel, sakbas, sarad, sbiarozk, sbunciak, sdawley, sdoran, sgehwolf, sghai, sidsharm, simaishi, slucidi, smallamp, solenoci, sostapov, sprizend, sseago, sskracic, stcannon, sthirugn, suppawar, syedriko, teagle, thason, thjenkin, tmalecek, tpfromme, tqvarnst, tsedmik, tsze, ttakamiy, twaugh, vdosoudi, vereddy, veshanka, vimartin, vkumar, vlaad, vvoronko, watson-tool-maintainers, weaton, xdharmai, xiaoxwan, yguenane, ykashtan, zzhou
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
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Doc Text:
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-06-19 20:01:18 UTC
urllib3 version 2.6.3 is vulnerable to a decompression bomb bypass in its streaming API (`preload_content=False`) when using Brotli support. The issue arises due to three independent code paths in `response.py` that bypass the `max_length` protection introduced in version 2.6.0 to mitigate CVE-2025-66471. Specifically, negative `max_length` values can be produced due to buffer arithmetic in `read()`, `flush_decoder` unconditionally overrides `max_length` to `-1`, and `_flush_decoder()` passes no limit at all, defaulting to unlimited decompression. This allows a malicious HTTP server to trigger an out-of-memory (OOM) condition by decompressing large payloads into memory, leading to a denial of service (DoS). The vulnerability affects urllib3 2.6.3 and Brotli 1.2.0 and impacts applications and libraries using `requests` or `urllib3` to stream content from untrusted sources.